U.S. patent application number 12/724290 was filed with the patent office on 2010-09-16 for rf radiation redirection away from portable communication device user.
Invention is credited to Robert Moreno, Karl Richard Shields, Rong Wang, Alfred Y. Wong.
Application Number | 20100234081 12/724290 |
Document ID | / |
Family ID | 42731143 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100234081 |
Kind Code |
A1 |
Wong; Alfred Y. ; et
al. |
September 16, 2010 |
RF RADIATION REDIRECTION AWAY FROM PORTABLE COMMUNICATION DEVICE
USER
Abstract
A case for a wireless device includes a number of RF coupling
elements mounted in the case and configured such that RF radiation
is coupled from an internal antenna of the wireless device out of
the device to a first RF coupling element, and from the first RF
coupling element to a RF redirector coupling element that redirects
the RF radiation in a direction outward from said wireless device
that is opposite to a user side of the wireless device. A
corrugated metallic shield is optionally provided on an opposite
side of the case, facing a user of the device.
Inventors: |
Wong; Alfred Y.; (Los
Angeles, CA) ; Moreno; Robert; (Acton, CA) ;
Shields; Karl Richard; (North Hills, CA) ; Wang;
Rong; (Sherman Oaks, CA) |
Correspondence
Address: |
NOVAK DRUCE DELUCA + QUIGG LLP
300 NEW JERSEY AVENUE NW, FIFTH FLOOR
WASHINGTON
DC
20001
US
|
Family ID: |
42731143 |
Appl. No.: |
12/724290 |
Filed: |
March 15, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12614132 |
Nov 6, 2009 |
|
|
|
12724290 |
|
|
|
|
61160282 |
Mar 13, 2009 |
|
|
|
Current U.S.
Class: |
455/575.5 ;
455/575.1 |
Current CPC
Class: |
H01Q 19/28 20130101;
H01Q 9/0407 20130101; H04B 1/3888 20130101; H01Q 1/245 20130101;
H01Q 19/005 20130101; H01Q 1/243 20130101; H01Q 7/00 20130101 |
Class at
Publication: |
455/575.5 ;
455/575.1 |
International
Class: |
H04M 1/00 20060101
H04M001/00; H04W 88/02 20090101 H04W088/02 |
Claims
1. A case for a wireless device, comprising a plurality of RF
coupling elements mounted in said case and configured such that RF
radiation is coupled from an internal antenna of said wireless
device out of said device to a first of said RF coupling elements,
and from said first RF coupling element to a RF redirector coupling
element that redirects said RF radiation in a direction outward
from said wireless device that is opposite to a user side of said
wireless device.
2. A case for a wireless device as set forth in claim 1, wherein at
least one of said RF coupling elements is configured as a loop.
3. A case for a wireless device as set forth in claim 1, wherein at
least one of said RF coupling elements is configured as a
horizontal strip.
4. A case for a wireless device as set forth in claim 3, wherein at
least one of said RF coupling elements is configured as a vertical
strip that functions in combination with a horizontal strip.
5. A case for a wireless device as set forth in claim 4, wherein
said vertical strip is mounted in a layer above a horizontal
strip.
6. A case for a wireless device as set forth in claim 1, wherein at
least one of said RF coupling elements is configured as a U-shaped
element.
7. A case for a wireless device as set forth in claim 1, wherein at
least one of said RF coupling elements is configured as a
plate.
8. A case for a wireless device as set forth in claim 7, wherein
said plate is rectangular in shape.
9. A case for a wireless device as set forth in claim 8, wherein
said plurality of RF coupling elements is configured as a ladder
and plate RF redirecting coupler.
10. A case for a wireless device as set forth in claim 1, wherein
said first RF coupling element is configured as a loop and said RF
redirector coupling element is configured as a loop.
11. A case for a wireless device as set forth in claim 10, wherein
said first RF coupling element loop is positioned over a side and
bottom of said wireless device so as to wrap around said internal
antenna.
12. A case for a wireless device as set forth in claim 1, further
comprising a metallic shield mounted in said case on a side facing
a user of said device.
13. A case for a wireless device as set forth in claim 13, wherein
said metallic shield is corrugated.
14. A case for a wireless device as set forth in claim 14, wherein
a size of corrugations of said metallic shield is smaller than
wavelengths of microwave frequencies transmitted from the wireless
device.
15. A case for a wireless device as set forth in claim 12, further
comprising a radiation absorbing material mounted adjacent to said
metallic shield between said shield and said user.
16. A case for a wireless device as set forth in claim 12, further
comprising a strip of dielectric material mounted between said
internal antenna and said metallic shield.
17. A case for a wireless device as set forth in claim 1, wherein
said first RF coupling element comprises a metallic sheet having a
slot formed therein of a length and width tuned to 1/4 of the
wavelength of RF transmission from said internal antenna.
18. A wireless device, comprising: a plurality of RF coupling
elements mounted in said wireless device and configured such that
RF radiation is coupled from an internal antenna of said wireless
device out of said device to a first of said RF coupling elements,
and from said first RF coupling element to a RF redirector coupling
element that redirects said RF radiation in a direction outward
from said wireless device that is opposite to a user side of said
wireless device.
19. A wireless device as set forth in claim 18, further comprising
a metallic shield mounted in said case on a side facing a user of
said device.
20. A wireless device as set forth in claim 19, wherein said
metallic shield is corrugated.
21. A wireless device as set forth in claim 20, wherein a size of
corrugations of said metallic shield is smaller than wavelengths of
microwave frequencies transmitted from the wireless device.
22. A wireless device as set forth in claim 19, further comprising
a radiation absorbing material mounted adjacent to said metallic
shield between said shield and said user.
23. A wireless device as set forth in claim 19, further comprising
a strip of dielectric material mounted between said internal
antenna and said metallic shield.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM FOR PRIORITY
[0001] This application claims benefit under 35 U.S.C. .sctn.119(e)
of copending provisional application Ser. No. 61/160,282 filed Mar.
13, 2009; this application is also a continuation-in-part of
copending application Ser. No. 12/614,132 filed Nov. 6, 2009; the
entire contents of which are incorporated herein by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to portable communication
devices such as cell phones, smart phones and similar handheld
devices, and improvements thereto. In particular, this invention
provides improvements in antennas and RF shielding of such devices,
facing a direction away from the user, to redirecting RF radiation
away from the body of a user.
[0004] 2. Background
[0005] Design requirements of cellular phones and smart phones are
placing an ever increasing premium on the available space within
these devices as their functions become more diverse, ranging from
the original basic function as a wireless telephone to a music
player, video player, handheld computer, wireless internet device
for browsing the web, retrieving email and downloading or uploading
files, a still camera, a video camera, a GPS device, a navigation
system, etc. These functions bring with them greatly increased
demands upon the antenna and generally requires more radiation
power for transmission, which must serve up to five frequency bands
while occupying less space than ever before available for the
antenna.
[0006] In addition, RF radiation from mobile phones is becoming of
greater concern as a health risk, and addressing this issue in the
design of the antenna while the space within the phone is reduced
poses a particularly difficult challenge, as the only effective
methods of significantly reducing RF radiation in the direction of
the user, while allowing full power RF signal away from the user,
require some additional space for the antenna.
[0007] The FCC requires limiting the radiation from a portable
communication device (such as a mobile or cellular telephone) that
is directed towards a user's head (Specific Absorption Rate, or
SAR). Each year the FCC tends to lower the permitted level further.
One of the reasons is safety. At the same time, as wireless
communications technology advances, the mobile phone device has
taken on the function of a hand-held computer with more
data-intensive functions, requiring high rates of data transfer
between the cell phone and the base station tower. It would be
beneficial to the improved function of cell phones to be able to
increase the power output of the antenna, but FCC regulations will
not allow increased SAR.
[0008] The Smart Phone (e.g. iPhone, BlackBerry, etc.), for
example, has an internal antenna(s) located at both the lower and
upper parts of the phone, bordering the display area. The space for
an antenna is usually limited to 1 cm times the width and thickness
of the phone. The antenna is situated close to the back surface of
the phone, on the side opposite to the user.
SUMMARY OF THE INVENTION
[0009] According to a first embodiment, a method of coupling
radiation from the antenna inside a wireless phone to a location
outside the device where the distribution of radiation can be
better managed. It presents several methods of directing RF
radiation away from the user's head by the appropriate placement of
metallic loops, directors and other parasitic elements. This can
take the form of arrays of monopole and dipole antennas, conducting
loops and conducting plates with insulators or dielectrics. The
general concept is to couple the radiation from the internal
antenna on the side facing the user to the opposite side to direct
such radiation outward away from the user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows RF coupling elements mounted on the back of a
mobile telephone.
[0011] FIG. 2 shows a perspective view of a mobile telephone with
placement of small and large antennas.
[0012] FIG. 3 shows an RF loop over an internal antenna of a mobile
telephone.
[0013] FIG. 4 shows an RF coupling parasitic device mounted on the
back of a mobile telephone.
[0014] FIG. 5 shows a front and side view of a "ladder and plate"
RF coupling design for a mobile telephone.
[0015] FIG. 6 shows an alternate embodiment of an RC coupling
parasitic device mounted on the back of a mobile telephone.
[0016] FIG. 7 shows a pair of RF coupling devices in the form of
first and second loops mounted on the back of a mobile
telephone.
[0017] FIG. 8 shows a partial phantom view of an RF coupling loop
design where the loop is mounted above the internal antenna of a
mobile telephone.
[0018] FIG. 9 shows a mobile telephone external case design
including a reflective shield at the front side of the device and a
radiation coupling device at the rear side of the device.
[0019] FIG. 10 shows an alternate embodiment of FIG. 9 wherein an
RF redirection system is integrated into the internal design of a
wireless device.
[0020] FIG. 11 shows an alternate embodiment of an RF loop design
mounted on the back of a mobile telephone device.
DETAILED DESCRIPTION OF THE INVENTION
[0021] In one preferred embodiment of the invention, external
coupling antennas are provided to couple radiation from the
internal antenna of a wireless device and to redirect the radiation
such that there is minimum radiation towards the user and maximum
radiation away from the user. It is important to note that this
coupling method does not require an actual physical connection
between the external coupling antennas and the antenna internal to
the phone. However the position of the coupling antenna with
respect to the internal antenna is critical. Through a series of
coupling loops, directing elements or patch antennas located on a
cover or case, a "clip" structure, or directly on an external
surface of the mobile device, the radiation is further directed
away from the user's head (which is absorptive) to the environment
for communication to cell towers.
[0022] The materials used for coupling and re-directional elements
are generally made out of materials of high electrical
conductivity. However dielectric materials are also used to achieve
optimal physical sizes and spacing of various elements.
[0023] The above methodology is illustrated by the treatment of two
exemplary wireless devices--the Apple 3G iPhone and the RIM
Blackberry Curve 8300. However the procedure is perfectly general
and can be applied to any wireless device using different
combinations of the elements described.
[0024] Referring to FIG. 1, the radiation from an internal antenna
(not shown) is directed away from the user and outward at the back
of the phone through a coupling loop 1 mounted on the back of the
phone. The coupling is achieved through electromagnetic (EM)
induction as revealed by laboratory experiments and computer
modeling of various physical quantities (antennas, connectors,
circuit elements, ground planes, etc.) inside a mobile
communication device such as an Apple iPhone, as illustrated in
FIG. 2. The EM fields are then successively coupled up a "ladder"
of metallic strips 2 up the backside of the iPhone enclosed inside
the case. The placement of the coupling loop 1 with respect to the
antenna inside the mobile device is critical. As shown, the
horizontal metallic strips may be straight, or may have regular or
irregular shapes such as "U" shaped metallic element 3, whose
dimensions are adjusted to fit the available space on the back of
the phone, while achieving optimal coupling from the loop 1.
[0025] One variation of the above design is in the replacement of
an uppermost radiation re-director by a single plate 3 as
illustrated in FIG. 3. The use of a plate resembles a patch antenna
whose radiation pattern favors the outward direction away from the
user. The loop 1 couples power out from the internal antenna, then
the directors 2 couple the power up to the plate 3, from which the
radiation is directed outward from the phone in the direction
opposite to the user's head.
[0026] Another variation, illustrated in FIG. 4, as well as in FIG.
5, which depicts an application of this design to the Apple iPhone
3G, is the replacement of the coupling loop by an RF coupling
parasitic redirector composed of horizontal strips 1 that form a
ladder-like array leading to a rectangular plate 2 above the
ladder. All these configurations have been tested and shown to
significantly reduce the amount of radiation directed towards a
user while maintaining or even enhancing the total radiation power
of the cell phone.
[0027] A further embodiment is the use of vertical strips 2 that
are orthogonal to the horizontal strips 1, as shown in FIG. 6.
These vertical strips couple to a vertical polarization of the
radiation from the internal cell phone antenna. The purpose is to
couple to both polarizations to fully redirect the maximum amount
of RF radiation from the cell phone antenna away from the direction
of the user. The vertical strips 2 are placed in a layer above the
horizontal strips such that they provide additional coupling with
any corresponding vertical elements of the internal antenna.
[0028] For some wireless communication devices, such as the
Blackberry 8300 shown in FIG. 8, the internal components of the
phone require a simpler approach as illustrated in FIG. 7, where a
single loop 1 is placed over the location of the internal antenna,
and may be augmented by a second loop 2 above the first loop 1. The
first loop 1 couples the RF field from the internal antenna, and
the second loop 2 provides additional redirected radiation away
from the user. Size and spacing are tuned to the particular phone.
For the Blackberry 8300, a loop of 24 mm.times.16 mm.times.2 mm is
placed such that it wraps under the bottom of the phone by 2 mm as
shown in FIG. 8. This configuration produces ideal results as
verified by independent laboratory testing by Cetecom in Milpitas,
Calif.
[0029] In another embodiment of the invention shown in FIGS. 9 and
10, a shield comprising a corrugated metallic surface is provided,
either incorporated into a protective case (FIG. 9), or integrated
directly into the body of the mobile communication device itself
(FIG. 10). The metallic shield is located on the user side of the
phone directly in front of the internal antenna. Such a shield also
may be installed inside the cell phone. Such a corrugated surface
gives rise to many image dipoles, thereby providing a wide pattern
of scattered radiation. The particular shape and size of
corrugations are designed to scatter radiation, which normally
would be incident upon the user, in directions away from the user
as widely as possible. In scientific terms the scattering angles
from the incident wave vector could range from +/-40 to +/-180
degrees.
[0030] The corrugations generally should have sizes smaller than
wavelengths of microwave frequencies transmitted from the wireless
device. They therefore introduce scattering wave vectors that are
greater than the incident wave vector in directions perpendicular
to the incident wave vector. The purpose of the design of the
corrugations is to deflect the radiation away from the user and at
the same time avoid creating reflections back on the internal
radiating antenna; as a result the impedance seen by the output
amplifier of the wireless device, e.g. the cell phone, is not
affected and the total radiated power of the phone is not reduced,
while SAR is significantly reduced.
[0031] In this embodiment, the loop 4 and the directors 6 are
positioned relative to the internal antenna 5 such that the loop is
close to the antenna and couples the RF power out from the back of
the phone and up to the directors 6.
[0032] As shown in FIG. 9, in a case 7, a layer of highly
conductive corrugated metal shield material 1 is, optionally,
combined with a layer of absorptive material 3 of a specific
frequency range, placed on the side of the metallic shield opposite
to the internal antenna, such that with the phone inserted into the
external case the shield is positioned between the user's head and
the internal antenna. The absorber 3 prevents any radiation that
passed through the shield from reaching the user. Also, a layer of
dielectric material 2 may be added between the internal antenna and
the shield to reduce the spacing required to achieve an effective
distance between the antenna and the shield of 1/4 wavelength of
the RF radiation.
[0033] The redirection of RF radiation away from the user's head
also may be achieved by the use of a properly located passive RF
coupling redirector 4-6 as shown in FIG. 9, in combination with the
corrugated shield of highly conductive metallic material 1. An
alternate embodiment as shown in FIG. 10 may have the RF redirector
4-6 and metallic shield 1 integrated within the wireless
communication device itself.
[0034] A main feature of this invention, both as a passive
directional beam antenna alone, or in combination with a passive
re-directional shield, incorporated in an external case for a
wireless phone, or such combination incorporated internally in a
wireless phone device, is that the invention directs/redirects
radiation away from the user, out of the phone, reducing SAR
(Specific Absorption Rate), without adversely affecting TRP (Total
Radiated Power). It does this with a directional antenna, or a
combination of a directional antenna and re-directive shield, or
with a re-directive shield only, integrated within a case of
non-conducting or low-conductive materials (variously of silicone,
plastic, cloth, etc.) that allow EM waves to propagate outward
toward the cell phone tower without suffering any attenuation.
[0035] A further alternate embodiment of the RF coupling radiation
redirector is shown in FIG. 11. Here, a loop 1 consists of a
metallic sheet with a narrow slot having a length and width tuned
to 1/4 of the wavelength of the transmitting RF radiation. For
example, a 1900 MHz transmission would correspond to a 40 mm slot
length.
* * * * *